fix: update empty-state event button label for users with past events

[Tharunraja7]

Fix for "Create your first event" label shown for users with past events (#409)

Updated the empty state logic in DashboardEventsPage.vue to display the correct button label based on whether the user has past events.

Changed the button label from a static value to a computed property.

Added a computed check for past events using summary.counts.past.

Before fix:

• Button always showed "Create your first event"

After fix:

• Shows "Create your first event" when there are no past events
• Shows "Create a new event" when past events exist

Closes #409

Before fix :

After fix :

[tompscanlan]

Code reviewed: types verified (DashboardEventCounts.past exists), NoContentComponent accepts buttonLabel prop, computed logic is correct. Clean single-file change.